This invention relates to a light source which is an incoherent or non-laser light source for use primarily but not exclusively in medical applications.
Lasers have widespread uses in the treatment of the human or animal body, which uses may be of a therapeutic and/or cosmetic nature. For example, laser light can be used to kill cancer cells or for treatment of portwine stains and removal of tattoos. However, medical lasers tend to have many disadvantages. Firstly, some medical lasers for certain requirements can cost up to a one hundred and forty thousand pounds or more and may require very bulky power supplies and/or bulky transformers in addition to involving complex or inconvenient cooling arrangements. Additionally, the power consumption by the laser may be very high and the laser itself may not be user friendly, for example, some lasers may require a one and a half hour warm-up time before they can be used in certain applications and may have a similar shut-off period. Often, the laser itself may be a far more sophisticated piece of equipment than is actually required for a particular task and therefore may be over suited to the task in hand. Some medical applications do not in fact require the critically offered by a laser although other acceptable light sources do not seem to have been developed to be used instead of a laser in such applications.
Non-laser light sources have been developed for medical applications but such proposals have tended to be inefficient and generally unsuitable for the task in hand. For example, a paper from the Journal of Photochemistry and Photobiology B: Biology 6 (1990) 143-148 on Photodynamic Therapy with Endogenous Protoporphyrin reports the use of a 500 watt filament light source for irradiation of cancerous cells. The light source was varied from 150 to 300 watts per square centimetre but spread over a very wasteful large bandwidth greater than 100 nm. The filtering tended to be inefficient and unsuitable giving rise to tissue damage from thermal effects.
Another proposal is discussed in the xe2x80x9cPhototherapy of Human Cancersxe2x80x9d in an article entitled Porphyrin Localisation and Treatment of Tumors, pages 693-708, 1984 Alan R. Liss, Inc. This article discusses the use of a filtered incandescent lamp having a 1000 watt filament source which is water cooled. The size of the apparatus itself is large and tends to be inefficient also entailing considerable risk of skin damage because of high flux density.
It is an object of at least some embodiments of the present invention to provide an incoherent or non-laser light source which at least alleviates one or more of the aforementioned, or other, disadvantages associated with lasers or which is more suited to the particular task in hand than a laser.
According to a first aspect of the present invention there is provided an incoherent or non-laser light source comprising a high intensity lamp, a bandpass filter and focusing means arranged to yield a light beam having an output intensity greater than 0.075 watts per square centimetre for a bandwidth in the range 0 to 30 nm and preferably in the range 0 to 25 nm.
Usually, the output intensity of said light source will be greater than 1 watt per square centimeters for a bandwidth usually in the range 20 to 25 nm.
Preferably, the light source is tunable over a range of at least 350 to 700 nm and usually over a range of 250 to 1100 nm.
Preferably, the output beam is focused sufficiently so that light can be delivered by way of an optical fibre means or bundle to its point of action and said beam may be focused down to a 6 mm or less diameter.
In one embodiment of the present invention, the light source may be arranged to yield a beam with an output intensity of 6 watts per square centimetre at a bandwidth of 20 to 25 nm. The lamp may be a metal halide lamp.
Alternatively, the lamp may be a high intensity high pressure xenon, short arc lamp or any lamp producing intense light over a continuous spectrum. It is envisaged that an extended light source such as a filament would not produce the required intensity due to filament diversions. In this context a short arc lamp would appear to be the best option yet available and may be for example of only 300 watts or 500 watts, but preferably less than 1 kw due to heat output and and arc length. Preferably, the beam divergence of the lamp is very low, for example in the order of 4xc2x0 FWHM with a beam stability preferably in the order of 1%. Preferably, the lamp is adapted (for example by coating various parts thereof) to remove ultra-violet (UV) radiation from the light beam emerging from a lamp window.
The focusing means, preferably, comprises an aspheric lens and said lens is preferably anti-reflection coated.
The bandpass filter may be at least 50% of 65% efficient and is preferably 80% efficient or greater (e.g. 91%) for light within the transmission bandwidth.
A dichroic xe2x80x9chot mirrorxe2x80x9d may be provided to remove infra-red radiation from the beam.
A variable attenuator grill may be provided in order to vary the power output of the light source.
The light source is, preferably, provided with a readily interchangeable output window incorporating a connection matching a connection on a fibre optic bundle. In this manner the window can be interchanged for one having a different sized connection for a different sized fibre optic bundle. The output window may be provided in a screw cap.
A preferable embodiment of the present invention provides a portable light source. The size of the light source may have overall dimensions of 15xe2x80x3 by 10xe2x80x3 by 6xe2x80x3. The light source may be provided with a power supply connected to the lamp (preferably a xenon arc lamp or metal halide lamp). A cooling fan is preferably provided at the rear of the lamp. The light source may comprise a control shutter positioned directly in front of the lamp (in an alternative arrangement the shutter may be provided inbetween the bandpass filter and the aspheric lens) and followed by a dichroic xe2x80x9chot mirrorxe2x80x9d or other means to remove infra-red radiation and then by the bandpass filter, aspheric focusing lens and variable attenuation means. The light source is preferably provided with a control panel at the front thereof in order to operate the control shutter for timed exposure as well as perhaps incorporating manual override switches. The light source is, preferably, tunable by replacement of the bandpass filter and/or dichroic xe2x80x9chot mirrorxe2x80x9d. If it is desired for the emergent beam to be in the infra-red region for example for treatment of hyperthermia the xe2x80x9chot-mirrorxe2x80x9d can be replaced with a cold mirror to filter out the visible light. Additionally, the bandpass filter may be changed for one allowing light of a greater bandwidth (for example 100 or 200 nm) to pass through.
Further according to the present invention there is provided a non-laser light source comprising one or more of the following features:
(a) means for supplying a (monochromatic) light beam suitable for delivery into a fibre optic bundle, said light beam having a sufficient intensity for a bandwidth useful in PDT (photodynamic therapy) and/or
(b) in cosmetic methods of dermatological treatment, means for supplying a light beam of an intensity of at least 100 mw per square centimetre for a bandwidth in the range 20 to 25 nm,
(c) means for providing a beam of intensity greater than 0.075 watts per square centimetre which is tunable in the range of 250 to 1100 nm,
(d) said light source being portable and air cooled,
(e) means for delivering a (monochromatic) light beam to fibre optic bundles having different connector sizes,
(f) a bandpass filter of 60 to 90% efficiency or greater in a narrow nanometer range (for example less than 25 nm),
(g) facility for interchanging bandpass filters of different characteristics,
(h) said non-laser light source being suitable for medical applications in particular treatment of tumours and/or delivery of light suitable for photo-inactivation of cancer cells containing a drug having an absorption level in a narrow nanometer bandwidth, for example lying in the range 20 to 25 nm.
Further according to the present invention there is provided a method of in vitro PDT, said method comprising delivering non-laser light of a sufficient intensity to kill cancer cells, preferably of an intensity greater than 0.075 W/cm2 and usually 10 to 200 mW/cm2 for a bandwidth in the range 20 to 25 nm.
Further according to the present invention there is provided a cosmetic method of treatment of dermatological conditions, for example comprising removal of portwine stains, tattoos or psoriasis, using an incoherent light beam from a non-laser light source emitting a high intensity beam having an intensity greater than 0.075 watts per square centimeters for a bandwidth in the range 0 to 25 nm, said beam preferably being deliverable by an optic fibre bundle, and said method preferably comprising pulsing said beam. For removal of portwine stains wavelengths of 575 nm may be used and for removal of tattoos wavelengths of 620 nm may be used. The method may involve the introduction of a drug into the body undergoing cosmetic treatment, said drug being selectively activated by light of a particular wavelength.
According to a further aspect of the present invention there is provided, a non-laser light source suitable for medical applications, which source is tunable over a bandwidth of 350 to 700 nm (preferably over a bandwidth of 250 to 1100 nm) and which is capable of focusing a light beam for fibre optic delivery at an intensity of 100 mW/cm2 for a bandwidth of 25 nm or less.
Preferably, said light source is capable of focusing a beam at an intensity of up to 9 W/cm2 for a bandwidth of 25 nm or less.
Usually, the light source will be provided with a timed exposure facility and it is advantageous for the beam to be as intense as possible below thermal dosage and hyperthermia limits (a few 100 mw/cm2) since this will reduce the exposure time required.